Air Quality: Air Quality Pollutants

Ozone Definition

Formula: o3

Chemical Structure: 000

What is Ozone?
Ozone is an odourless, colourless gas at ambient concentrations and is one of the main components of smog.

What are the sources of ozone?
Ground-level ozone is not released straight into the atmosphere. It comes from photo-chemical reactions between nitrogen oxide (Nox) and volatile organic carbons in the presence of sunlight. From May to September, between noon and early evening are when high levels of ozone usually occur.

How does ozone affect people and the environment?
O3 causes irritation to the respiratory tract and to eyes. Contact with high levels of ozone can lead to chest tightness, coughing and wheezing. When exposed to ozone people that have respiratory or heart problems are at a higher risk. Ozone has been connected to increased hospital admissions and premature death. Ozone also has an impact on agriculture and crops.

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Nitrogen Dioxide Definition

Formula: NO2

Chemical Structure: ONO

What is Nitrogen Dioxide?
Nitrogen Dioxide is gas that is reddish-brown in colour and has a strong and irritating smell. In the air, nitrogen dioxide converts to form gaseous nitric acid and toxic organic nitrates. NO2 also plays a large part in atmospheric reactions that create ground level ozone, a main part in the makeup of smog. It is also a predecessor to nitrates which add to increased respirable particle levels in the atmosphere.

What are the sources of Nitrogen Dioxide?
All combustion in the air (ie car exhaust) creates oxides of nitrogen (Nox), of which NO2 is a major product. Natural sources of Nox include lightning and the aerobic activity of soil bacteria. However, these natural sources of emission are minor compared to those created by human activity.

How does Nitrogen Dioxide affect people and the environment?
Nitrogen dioxide can aggravate the lungs and reduce resistance to respiratory infection. For people with asthma and bronchitis an increase in sensitivity occurs. NO2 chemically changes into nitric acid and, when deposited contributes to lake acidification. Once chemically changed to nitric acid, nitrogen dioxide can corrode metals, fade fabrics, and degrade rubber. It can damage trees and crops, resulting in great losses.

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Suspended Particles Definition

What are suspended particles?
Suspended particles in the atmosphere are comprised of either solid particles or fine liquid droplets. Included in this group are: aerosols, smoke, fumes, dust, fly ash and pollen. The exact make up varies with both place and season. Particles in the atmosphere have been categorized based on size mostly because of the different health affect from particles of different diameters.

Particles with diameters of less than 100 microns (millionths of a metre) are classified as total suspended particles (TSP). In order to visualize how small a micron is, one micron is approximately the size of a single bacteria. Particles that are less than 10 microns and 2.5 microns are defined as inhalable particles (PM10) and respirable particles (PM2.5), respectively. The tinier the particle size, the further that particle will penetrate into the lungs.

What are the sources of suspended particles?
The bulk of the particle emissions from human activity can be categorized as TSP (total suspended particles).

Particles come from both natural and man made sources. Some of the natural sources include: windblown soil and mineral particles, volcanic ash, sea salt spray, and biological materials such as pollen, spores, bacteria and smoke from forest fires. The man-made sources result in both coarse and fine particles. Coarse particle matter comes from wind blown dust from agricultural soil, roads and construction sites. Smaller particles are created by the combustion of fossil fuel, residential heating and other sources as well. They can be released directly from a given source or formed in the atmosphere through the transformation of gaseous emissions. The composition of the particles varies with place, season, meteorology and daily weather.

How do suspended particles affect people and the environment?
The greatest effect on health comes from particles 10 microns or less in diameter PM10. Particles in this range can irritate bronchitis, asthma and other respiratory diseases. In some cases these small particles have been connected to greater hospital admissions and premature death. Those people that are most susceptible to the effects of particles include: those with asthma, cardiovascular or lung disease, as well as children and the elderly. Particles also cause corrosion, soiling damage to vegetation and visibility reduction.

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Total Reduced Sulphur Definition

What are total reduced sulphur compounds?
Total reduced sulphur compounds create strong odours reminiscent of cabbage or rotten eggs.

What are the sources of TRS?
Industrial sources such as the steel industry, pulp and paper mills, refineries and sewage treatment facilities are all contributors. Natural sources of TRS include swamps, bogs and marshes.

What effect does TRS have on people and the environment?
Usually TRS compounds are not considered to be a health hazard. TRS compounds are one of the main causes of odours.

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Sulphur Dioxide Definition

Formula: So2

Chemical Structure: OSO

What is sulphur dioxide?
Sulphur dioxide is a colourless gas that smells like burnt matches. It can be oxidized to form sulphur trioxide. Which in the company of water vapour is easily changed to sulphuric acid mist. SO2 can be oxidized to form acid aeorsols. Sulphur dioxide is the predecessor to sulphates, which are one of the main components of respirable particles in the atmosphere.

What are the sources of sulphur dioxide?
Industrial sources of this gas include iron and steel mills, petroleum refineries and pulp and paper mills. Small sources include residential, commercial and industrial space heating.

What are the effects of Sulphur Dioxide on people and the environment?
Being exposed to high levels of SO2 can cause breathing problems, respiratory illness, changes in the lung's defences, and worsening respiratory and cardiovascular disease. People that are most sensitive to sulphur dioxide are those with asthma or chronic lung or heart disease. It also causes damage to trees and crops. Sulphur Dioxide, along with Nitrogen Oxides, are the precursors of acid rain. This adds to the acidification of lakes and streams, accelerated corrosion of buildings and a reduction in visibility. Sulphur Dioxide also leads to the formation of microscopic acid aerosols, which has a major impact on health as well as contributing to climate change.

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Carbon Monoxide (CO) Definition

What is Carbon Monoxide?
CO is a colourless, odourless and tasteless but poisonous gas produced primarily by incomplete burning of fossil fuels.

What are the sources of CO?
The transportation sector accounts for 65 per cent of all CO emissions from human activity in Ontario as seen in the table and diagram below. A large part of the remainder comes from primary metal producers (24 per cent) and from fuel combustion in space heating and industrial processes (6 per cent).

What are the effects of CO?
CO enters the blood stream and reduces oxygen delivery to the organs and tissues. People with heart disease are particularly sensitive. Exposure to high levels is linked with impairment of vision, work capacity, learning ability and performance of difficult tasks.

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